by Jason Wasserman MD PhD FRCPC and Zuzanna Gorski MD
January 3, 2024
Low grade papillary urothelial carcinoma is a type of cancer that starts in a part of the body called the urinary tract. The urinary tract includes the kidneys, bladder, ureters, and urethra. Most tumours are found in the bladder. Pathologists divide this type of cancer into non-invasive and invasive based on the presence of tumour cells in the tissue below the urothelium, a thin layer of tissue on the inside surface of the urinary tract. This distinction is important because non-invasive tumours are typically cured through surgery alone while patients with invasive tumours may require additional treatment after surgery.
This article will help you understand your diagnosis and your pathology report for low grade papillary urothelial carcinoma.
The urinary tract
The urinary tract is a system designed to help remove waste and excess water from the body through the production of urine. The urinary tract includes the kidneys, ureters, bladder, and urethra. Urine made in the kidneys flows into the bladder by way of the ureters. The bladder stores the urine until it is released from the body by way of the urethra. The inside surface of the entire urinary tract is lined by specialized urothelial cells that form a barrier called the urothelium.
What are the symptoms of low grade papillary urothelial carcinoma?
Symptoms of low grade papillary urothelial carcinoma include bloody urine (hematuria), pain when urinating (dysuria), and the need to urinate more frequently.
What causes low grade papillary urothelial carcinoma?
Studies have shown that a wide variety of toxins, medications, and infections are associated with an increased risk of developing papillary urothelial carcinoma. Toxins that can cause this type of cancer include tobacco smoke, opium, benzidine-based dyes, aromatic amines, arsenic, and aristolochic acid produced by Aristolochia plants (which are commonly used in herbal medications). Chronic (long-term) inflammation in the bladder caused by infections such as the Schistosoma haematobium, prolonged indwelling catheter, and some medical treatments including radiation to the pelvis and chemotherapy with chlornaphazine or cyclophosphamide are associated with an increased risk of developing this type of cancer in the bladder.
Low grade papillary urothelial carcinoma
Low grade papillary urothelial carcinoma starts from the urothelial cells normally found in the urothelium, a thin layer of tissue that covers the inside surface of the urinary tract. Although this tumour is most commonly found in the bladder, it can arise anywhere along the length of the urinary tract. The tumour is described as low grade because the tumour cells look very similar to normal, healthy urothelial cells when examined under the microscope. As the tumour grows it forms long finger-like projections of tissue that stick out from the inside surface of the tissue. Pathologists use the term papillary to describe this pattern of growth.
Noninvasive and invasive tumours
Most low grade papillary urothelial carcinomas are non-invasive which means that the tumour is confined to the urothelium on the inside surface of the urinary tract. Non-invasive tumours are unable to spread to other parts of the body and are cured by surgery alone.
However, some tumours evolve into invasive tumours which means that the tumour has spread into the tissue below the urothelium (for example, the lamina propria or muscularis propria). Unlike non-invasive tumours, invasive tumours can spread to lymph nodes and other parts of the body.
When examining an invasive low grade papillary urothelial carcinoma, your pathologist will try to determine how far the tumour cells have spread into the layers of tissue below the urothelium. This information is very important because tumours that invade deeper into the surrounding tissue are more likely to spread to other parts of the body. This information is also used to determine the pathologic tumour stage (pT).
How is this diagnosis made?
The diagnosis is usually made by looking at a urine sample under a microscope. The diagnosis can also be made after a small sample of tissue is removed from the urinary tract during a procedure called a biopsy. After the diagnosis is made, the entire tumour is usually removed in a procedure called transurethral resection (TURBT). For larger tumours that involve the bladder or kidney, part or all of the organ may need to be removed in a procedure called a resection.
Why is it important to sample the muscularis propria?
The muscularis propria is a thick layer of muscle inside the wall of the bladder. When doctors remove a tumour in the bladder, they try to remove some of the underlying muscularis propria at the same time. Sampling of the muscularis propria is important because pathologists cannot rule out muscle-invasive disease until the muscle is examined under the microscope. For this reason, after a TURBT is performed, most pathology reports will say whether muscularis propria was seen or not in the tissue provided.
Can the tumour grow back after it is removed?
Yes. Approximately 50% of low grade papillary urothelial carcinomas will grow back after being removed. This is called a recurrence. Some tumours can change over time into a more aggressive type of cancer called high grade papillary urothelial carcinoma.
Pathologic stage
The pathologic stage for this type of cancer is based on the TNM staging system, an internationally recognized system created by the American Joint Committee on Cancer. According to this system, all low grade non-invasive papillary urothelial carcinomas are given a tumour stage of pTa.
About this article
This article was written by doctors to help you read and understand your pathology report. Contact us if you have any questions about this article or your pathology report. Read this article for a more general introduction to the parts of a typical pathology report.
Other helpful resources
Atlas of Pathology
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